Ring or racetrack waveguide resonators are commonly used in integrated photonic circuits as modulators or filters for optical signals. As such, the resonant frequency, usually denoted in terms of wavelength, of the waveguide resonator needs to align with the wavelength of the expected optical signals passing there through, otherwise the modulator or filter performance will be degraded.
The operating wavelength of such resonators can be sensitive to operating conditions such as temperature changes, which can cause wavelength drift. In order to compensate for such thermally induced wavelength drifts, a local micro-heater can be used to maintain a constant temperature of the waveguide resonator. When a waveguide resonator is locally heated, the heating causes a change in the effective refractive index of the waveguide resonator and produces a stable operational wavelength. The heater holds the waveguide resonator at a desired temperature and thus at a desired operating wavelength.
The heat-based drift compensation mechanism has considerable drawbacks such as slow response, extra energy costs, low accuracy, unidirectional heating only (no cooling down) and is difficult to be applied for practical use in integrated photonic systems.
What is needed is an improved wavelength drift compensation method and apparatus for photonic waveguide resonators.